Diclofenac, 2-(2,6-dichloro-anilino)-phenyl-acetic acid, is known as a non-steroidal anti-inflammatory drug (NSAID). NSAIDs produce their therapeutic activities through inhibition of cyclooxygenase (COX), the enzyme that makes prostaglandins (PGs). COX-1 makes PGs that protect the stomach and kidneys. COX-2 produces PGs that cause pain and inflammation. Diclofenac is a non-selective NSAID that inhibits both types of COX enzymes1.
The analgesic properties of diclofenac make it effective in cases of moderate to severe pain where rapid relief is required. Diclofenac is used to treat a wide range of musculoskeletal disorders, including muscular aches, sprains, strains, tendonitis (tendon inflammation), bursitis, bruises, fractures and dislocations. It is effective in the treatment of joint disorders, including arthritis, osteoarthritis (a degenerative joint condition), rheumatoid arthritis (inflammation of the joints), ankylosing spondylitis (an inflammation of the vertebrae), and pyrophosphate arthropathy (crystal deposits in the joints).
Diclofenac is also used to provide relief for those who suffer from acute gout, lower back pain, migraine headache, menstrual pain and dysmenorrhoea. It can alleviate the discomfort associated with inflammatory infections of the ear, nose, or throat, post-operative pain or inflammation due to trauma following dental, orthopaedic, or other minor surgery.
Diclofenac is available in solid dose formulations. The commercially available oral pharmaceuticals are formulated for rapid-acting effect. However, it is recommended to avoid taking them on an empty stomach as they have side effects such as stomach discomfort. When they are taken after eating, the initial absorption of diclofenac is outstandingly reduced in the amount and delayed in the rate compared with the case where they are taken on an empty stomach, and in some cases, the maximum absorption is confirmed at several hours to ten and several hours after taking them, and also individual difference is large in the absorption thereof. Rectal suppositories provide a more reliable rapid-acting effect, but there are many patients who are reluctant to use the suppositories.
Diclofenac is also available in topical formulations such as gels and patches. Gels require special handling and care, and can be less convenient to use as they interact with clothing and water. The commercially available patch is comprised of an adhesive material containing 180 mg of diclofenac epolamine in an aqueous base and measures 10 cm×14 cm (about 4 inches by 5.5 inches). The recommended dose is to apply one patch to the most painful area twice a day.
Consequently, today there is a strong request for diclofenac in forms providing convenience, fast effect and delivery certainty. The objective is to develop a daily, and more preferably a multi-day, single-dose transdermal delivery device.